Advanced find A well-preserved set of 1.98-million year old fossils may change our views of the origins of humans, by showing a combination of anatomical features never seen before.

The fossils, believed to be from the hominid species Australopithecus sediba, are described in a series of papers that appear today in the journal Science.

"The many very advanced features found in the brain and body ... make it possibly the best candidate ancestor for our genus, the genus Homo, more so than previous discoveries," says Professor Lee Berger, at the Institute for Human Evolution at the University of the Witwatersrand in Johannesburg.

Since the discovery of the site by Berger and James Cook University researcher Professor Paul Dirks in August 2008, 220 bones have been found, representing at least five individuals.

Among the collection was the most complete hand, as well as an undistorted hip bone and well-preserved ankle bones.

"This is giving us insight, that isn't guesswork into an area of anatomy that is crucial and critical in how human walking evolved," says Berger of the foot and ankle bones.

The hand, which was described as being human-like at the end of an ape-like arm, had a precision grip that could have aided in making tools, says team member Tracy Kivell, a researcher at Germany's Max Planck Institute.

Its elongated thumb differs from that of apes and allows for it to grasp objects more firmly.

The grapefruit-sized brain of A. sediba is similar in shape to that of humans, and may challenge theories about brain enlargement in human development.

Highly accurate dating

The highly accurate dating of the samples was made by scientists based in Australia.

Dr Robyn Pickering led a team of researchers at the University of Melbourne's School of Earth Sciences, who conducted uranium lead dating of the flowstone surrounding the fossils.

She says researchers have long been searching for fossils from this time period to answer questions about the beginnings of our own genus Homo.

"Knowing the age of the fossils is critical to placing them in our family tree, and this new age means that A. sediba is the current best candidate for our most distant human ancestor."

"The results of these studies present arguably the most precise dates ever achieved for any early human fossils."

Dr Andy Herries from La Trobe University in Melbourne undertook the palaeomagnetic analysis of the samples, which used known reversals in the Earth's magnetic field to assisting in dating.

"It dates to this really, really short period of time which is perhaps 3000 years which is pretty amazing because it's so rare to find these basically little tiny geomagnetic field flips," says Herries.